$-\dfrac{9}{4} + \dfrac{7}{2} = {?}$
Explanation: $ = - {\dfrac{9 \times 1}{4 \times 1}} + {\dfrac{7 \times 2}{2 \times 2}} $ $ = - {\dfrac{9}{4}} + {\dfrac{14}{4}} $ $ = - \dfrac{{9} + {14}}{4} $ $ = \dfrac{5}{4}$